The present invention is directed to polymeric compounds suitable as initiators for polymerization reactions. More specifically, the present invention is directed to polymeric compounds based on triphenyl sulfonium salt units which are useful in several polymerization applications, such as curable coatings and curable liquid developers. One embodiment of the present invention is directed to polyesters and polycarbonates of the formulae ##STR2## wherein X is an anion with weak nucleophilicity, A, B, and C represent the number of monomer units, wherein C may be zero, R is selected from the group consisting of hydrocarbon groups and alkylene ether groups, and R" is selected from the group consisting of hydrogen, nitro, amide, halide, trimethylsilyl, alkyl groups, and alkoxy groups.
Polymeric compounds useful as polymerization initiators are known. For example, polystyrene based iodonium compositions and polyimide/triphenyl sulfonium compounds have been described as useful initiators by Crivello et al., Journal of Polymer Science: Part A: Polymer Chemistry, vol. 25, 3293-3309 (1987) and Crivello et al., J. L. Polymer Bulletin, vol. 16,243-248 (1986), the disclosures of each of which are totally incorporated herein by reference. The major advantages associated with these initiators include low toxicity and low volatile by-product from the curing process. The synthesis of these polymeric initiators, however, is very complicated, requiring multistep syntheses.
U.S. Pat. No. 4,840,977 (Crivello et al.), the disclosure of which is totally incorporated herein by reference, discloses photosensitive iodonium polymers which are useful as positive photoresists. The iodonium polymers can be converted to polymeric diaryl iodonium polyfluorometal and metalloid salts by a metathesis reaction. The polymeric iodonium polyfluorometal and metalloid salts can be used as a catalyst in combination with a copper compound cocatalyst to make heat curable compositions with cationically polymerizable materials such as an epoxy resin.
U.S. Pat. No. 4,264,703 (Crivello), the disclosure of which is totally incorporated herein by reference, discloses cationic polymerization of a variety of organic materials such as vinyl monomers, prepolymers, cyclic ethers, cyclic esters, and organosilicon cyclics by the use of certain radiation sensitive aromatic halonium salts. In addition, polymerizable compositions are provided which can be used as coating compounds, molding resins, and adhesives.
U.S. Pat. No. 3,989,644 (Bolon et al.) discloses a radiation curable ink which is convertible to a conductive coating when cured on the surface of a substrate. A non-ionic surfactant is used in the curable ink in combination with a particulated metal containing conductive filler and an organic resin binder. As a result of using the non-ionic surfactant, a reduction was achieved in the tendency of the curable ink to form two distinct layers based on the separation of the conductive filler from the organic resin binder.
U.S. Pat. No. 4,933,377 (Saeva et al.)discloses sulfonium and oxysulfonium salts useful as photoinitiators which have directly attached to the sulfur atom thereof at least one aromatic or heterocyclic aromatic substituent containing at least 14 aromatic atoms and having a removable positive hydrogen ion, said substituent exhibiting a higher energy occupied molecular orbital than at least one other substituent directly attached to the sulfur atom, and at least one substituent comprising an electron withdrawing group and exhibiting a lower energy unoccupied molecular orbital than at least one other substituent directly attached to the sulfur atom, the salt being capable, upon exposure to visible radiation, of undergoing irreversible intramolecular rearrangement to form a Bronsted acid comprising the anion of the salt add the removable positive hydrogen ion.
Although known compositions and processes are suitable for their intended purposes, a need remains for polymerization initiators suitable for use in processes where liquids are cured to solids. In addition, a need remains for polymeric polymerization initiators that are easy to synthesize. Further, a need remains for easily synthesized polymerization initiators that enable rapid photo curing or thermal curing of materials such as vinyl ethers and epoxies. Additionally, there is a need for polymerization initiators that are insoluble in or of low solubility in the curing materials which are useful for curable liquid developers.